Measuring and display system

ABSTRACT

Apparatus for measuring and displaying the amount and degree of movement of a movable element of a machine tool comprising a linear member and a rotatable member angularly disposed thereto and in surface engagement therewith. Either or both of the members is displaceable in correspondence with the movable machine element so as to cause rotation of the rotatable member by interaction of the surface engagement. The rotatable member is provided with means for producing a signal indicative of the incremental rotation thereof. The signal is fed to a display device whereon the degree of displacement from an initial position can be seen.

[ 1 Sept. 5, 1972 United States Patent Zeidler et a1.

[54] MEASURING AND DISPLAY SYSTEM 2,994,959 8/1961Thomas....................33/141.5 [72] Inventors: Herman RudolfZeidler, 3,494,039 2/1970 Porter..........................33/l42 FOREIGNPATENTS OR APPLICATIONS sapequa Park; Ronald M. Aurnou, Deer Park, bothof NY.

[73] Assignees Linear Motion Technology, Inc.,

557,069 11/1943 GreatBritain..........33/l25M 139,185 2/1953Sweden...................33/125M Farmingdale, NY.

April 15, 1970 Appl. No.: 28,783

Primary Examiner-William D. Martin, Jr. Attorney-Bauer & Amer 221 Filed:

ABSTRACT Apparatus for measuring and displaying the amount and degree ofmovement of a movable element of a machine tool comprising a linearmember and a [30] Foreign Application Priority Data Aug. 26, 1969 GreatBritain..........42,375/69 rotatable member angularly disposed theretoand in [52] U S Cl 33/ 33, 3}; surface engagement therewith. Either orboth of the [58] Field of SearchM33/l42 125 M R 141 B members isdisplaceable in correspondence with the [51] Int.

33/141 E 1415 141 movable machine element so as to cause rotation of therotatable member by interaction of the surface engagement. The rotatablemember is provided with [56] References Cited UNITED STATES PATENTSmeans for producing a signal indicative of the incremental rotationthereof. The signal is fed to a display device whereon the degree ofdisplacement from an initial position can be seen.

3,449,833 6/1969 Dzula..................33/l25 M X 2,663,598 12/1953Verderber................33/141 R 25,423 9/1859 Lafever.......................33/142 7 Claims, 11 Drawing Figures PATENTEDSEPI5 m2 SHEEI 1 0F 3 INVENTORS RONALD M. AURNOU HERMAN R. ZEIDLER FIG.6

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AT TURNEYS PATENTEDSEP m 3.688.410

SHEET 2 0F 3 RONALD M. AURNOU HERMAN R.ZEIDLER A T TORNE YS rmmtnw' 5Ian 3.688.410

sum 3 or 3 1' 4.4 '2 FIG. IO

FIG. I!

INVENTORS. RONALD M. AURNOU HERMAN R. ZEIDLER BY @Wfl y ATTORNEYSMEASURING AND DISPLAY SYSTEM The present invention relates to machinetool controls and in particular to apparatus for metering and displayingthe amount or degree of movement of the movable element of said tools.

Machine tools such as planars, millers, lathes, etc., engage in a seriesof cyclical operations in which the movable element repeats its functionon a successive number of work-pieces. It is of course preferred andmost desirable that each work-piece be finished as close as possible inan identical manner with the others and, therefore, controls must beprovided which enable the machine operator to obtain this result.However, as is well known, machine parts wear and erode after continuoususe. The movable machine element warps, bends and also gets out of lineso that after a short while errors creep into the repetitive operation.This is a particular troublesome problem in connection with thedefinition of the starting or reference point at which the machine maybegin its cyclical operation.

Conventionally, the initial position or the fixed reference point of themovable element has been obtained by establishing a corresponding fixedinitial position of the movable machine tool element with a definedpoint on the immovable portion of the machine. To this end the movingtool element itself, its lead or drive screw or some other portion ofthe movable portion of the machine has been employed. This technique iseffective when the machine is new and properly adjusted; however, assoon as the slightest degree of wear occurs, the matching of thereference points is no longer truly indicative of the original andinitial reference location.

It is, therefore, the object of the present invention to provideapparatus for the measuring and display of the amount and degree ofmachine tool movement overcoming the prior art drawbacks.

It is another object of the present invention to provide for themeasuring and the display of the movement of the machine toolirrespective of a fixed reference point.

It is another object of the present invention to provide apparatus fordisplaying the movement of a machine tool in alpha-numeric logic.

It is a specific object of the present invention to provide apparatuswhich is free of the effects of wear, erosion or other distortions ofthe machine tool.

In summary, the present invention provides a measuring and displaydevice for a machine tool comprising a linear member and a rotatablemember angularly disposed thereto and in surface engagement therewith.Either the linear or rotatable member is displaceable in correspondencewith the movable element of the machine tool so as to thereby causerotation of the rotatable member by interaction of the surfaceengagement. The rotatable member is provided with means for producing asignal indicative of the incremental rotation thereof which signal isfed to a display device for visually displaying the degree ofdisplacement from an initial starting point.

Further, in accordance with the present invention the linear member andthe rotatable member are resiliently urged against each other so as tobe maintained in continuous surface engagement and the rotatable memberis provided with an annular disc having coding means capable of beingsensed by a photoelectric cell. In one embodiment, the rotatable member,the coding means thereof and the photocell are mounted in common so asto be jointly movable. In other embodiments, the mounting of theseelements is modified so that various arrangements of conjoint andnon-joint movement are affected.

The full details of the present invention, its structure and itsoperation together with an illustration of the objects and advantages iscontained in the following description which refers to the accompanyingdrawings in which:

FIG. 1 is a schematic perspective view of the metering and displaydevice of the present invention;

FIG. 2 is a cross-sectional view of the measuring portion of theapparatus of FIG. 1 taken along lines 2-2 of FIG. 3;

FIG. 3 is a sectional view taken along lines 33 of FIG. 2;

FIG. 4 is a sectional view taken along lines 44 of FIG. 2;

FIG. 5 is a sectional view similar to FIG. 3 showing a modification ofthe invention;

FIG. 6 is a sectional view similar to FIG. 2 showing the modification ofFIG. 5 at a different angle;

FIGS. 7-9 are sectional views similar to those above showing stillanother embodiment of the present invention; and

FIGS. 10-11 are sectional views also similar to those previouslymentioned showing yet a third embodiment of the present invention.

Before turning to a full description of the present invention, it willbe understood that it may be applied to a variety of machine tools andis not limited to any one in particular. However, for illustrationpurposes, the embodiment shown herein and described is particularlysuitable for application to a milling machine having a table on which awork-piece is operated on. The table, as is well known, can eitherreciprocate, oscillate or otherwise move within a defined plane and maybe placed in repetitive motion by the machine operator or automaticallyby suitable control means. A milling machine also has a second movablemember comprising the cutter or other operative tool which may bemovable in an axis or in a plane angular to the table. As illustratedthe present invention may be applied to either the table or to thecutter of the milling machine, as will be easily and obviouslyunderstood by anyone skilled in this art. The milling machine, table,cutter and other drive operative means are not shown or described anyfurther in the present description since these are well known and theirstructure and function, if elaborated on herein, will only be redundantand repetitious of the information freely available.

Referring now to FIG. 1 of the drawings, the numeral 10 generallyidentifies the combined measuring and display device which comprises ameasuring rod or suitable linear member 12 that is adapted to be fixedlymounted to a part of a machine with which the present invention isadapted to operate, as for example the table of a milling machine. Whilethe axis at which the rod 12 is mounted is not critical, it will beappreciated that it is to be secured to the moving machine element so asto be displaced correspondingly with it. The rod 12 is of a hardenedmaterial that is precision ground and accurately engages a meteringroller 14. In the diagrammatic representation shown in FIG. 1, themetering roller 14 is connected in a one to one direct drive ratio witha rotatable disc 16. The connection 18 between the metering roller 14and disc 16 may be a solid drive shaft or a flexible connection,depending upon the relative locations and positioning of the respectivemembers.

The disc 16 is provided with a series of coding means that may be in theform of calibrations, slots or indices 20 thereon which are rotativelymoved relative to and for sensing by an encoder structure comprising alight source 22 and a photo pick-up 24 that is responsive to the sensingof the relatively moving coding means 20. Each movement of the codingmeans 20 relative to the combined photo pick-up 22, 24 produces anelectrical signal or pulse that is received by a multiplier and pulseshaping amplifier apparatus of conventional construction identified bythe numeral 26. The shaper and amplifier shapes and amplifies and, inturn, imparts the information signal or pulse to a digital counter 28containing a plurality of display windows 30 in which the precisemeasurement information may be displayed to the machine operator.

Referring now to FIGS. 2, 3 and 4 wherein the measuring and displaydevice is illustrated in working operation, the linear measuring member12 is adapted to be mounted by conventional means on any convenientsurface of a machine or other apparatus with which the present inventionis intended to be utilized. As noted previously, the rod 12 may bepositioned in any desired axis. Generally, it is the practice toposition the rod along that part of the machine which is to move or tobe moved relative to another portion or part of the same machine andwith the axis of the rod substantially parallel to the direction ofmovement. In this regard, the metering roller 14 that is adapted toengage and have movement relative to the measuring rod 12 may bepositioned on another part of the machine and in an arrangement angularto the axis of the rod 12 so that movement of the rod in a lineardirection causes rotation of the metering roller 14 about its own axis.It is possible that the rod 12 may be placed upon one part of themachine while the metering roller 14 may be mounted on another part ofthe machine by mere conventional rearrangement of the parts. It isentirely possible that either one of rod 12 or metering roller 14 may bestationary while the other may be relatively movable or both may bemounted on movable parts of the machine for displacement relative toeach other.

With the rod 12 fixed to a moving part of the machine, the roller 14 isadapted to be mounted to another part of the machine by containing itwithin a housing generally identified by numeral 32. The housing 32defines a substantial and almost complete enclosure for the partsassociated with the metering roller. The housing 32 includes a rear wall34, a top'wall 36, a bottom wall 38 and end walls 40 and 42. Each of therear, top and bottom walls 34, 36 and 38 respectively are provided withoutward extensions or bosses 44 which may be provided with planarsurfaces that are relatively smooth so as to enable the housing 32 to beconveniently mounted to a part of the machine by positioning it on suchmachine part at the respective surfaces 44.

Enclosed within the housing 32 is a pivot yoke or a housing member 46that has spaced top and bottom arms 48 connected by the rear wall of theyoke. Each of the arms 48 is provided with a bearing structure 50 inwhich is mounted the narrowed shaft ends 52 of the metering roller 14.

The metering roller 14 is connected with the rotatable disc 16 by theextension of the lower shaft end 52 of the metering roller 14. The lowerend of shaft 52 of the metering roller 14 may be directly connected withthe disc 16 or it may be joined thereto by a coupling element 54. Thecoupling element 54 may be flexible in construction in the event therelative positions of the disc 16 and the metering roller 14 are out ofaxial alignment. In the embodiment of FIGS. 2-4, it has been foundconvenient to provide the coupling element 54 as a fixed mechanicalconnection between the lower end 52 of the metering roller 14 and thedisc 16.

The yoke 46 carrying the metering roller 14 and the connected disc 16 ispivoted within and relative to the interior of the housing 32 and alsorelative to the measuring rod 12 at a pivot shaft 56 that is mountedtransverse to the axis of the rod 12, at one end in the front wall 36 ofthe housing 32 and at its rear end in a lip extension 58, extendinglaterally inward from the end wall 42. The yoke member 46 is constantlybiased in a direction to move the metering roller 14 for positiveengagement with the measuring rod 12 by a coil spring 60. In this mannerthe metering roller 14 is held against the surface of the measuring rod12, even though the measuring rod 12 may flex, bend, shift or otherwisemove axially to its longitudinal axis or axis of operative movement.

The spring 60 is seated within a counterbore 62 defined in a lateralextension 64 of the yoke. The opposite end of the spring 60 is seatedand retained within a through hole 66 provided in the upper wall 36, asseen in FIG. 2. The hole 66 is closed by a threaded plug 68. Threadedadjustment of the plug 68 into and out of the hole 66 will result invarying the tension applied by the spring 60 against the yoke 46 andthus will enable a fine and precise adjustment of the pressure withwhich the metering roller 14 engages the measuring rod 12.

Fixed for conjoint movement with the yoke 46 is the photo pick-up andlight sensing composite structure 24, 22. This is afforded by connectingthe light and photo pick-up 22, 24 units to the yoke 46 on upwardlyextending arm 70 defined at the rear face of the yoke. A pair of screws72 are conveniently employed to connect such structures together forconjoint movement.

The light sensor and photo pick-up structure 22, 24 extends into andforms a part of a sub-assembly including sub-housing 74 that also isconveniently secured to and moves conjointly with the yoke 46. Thesub-housing 74 is closed at its side by a plate 76 through which thebottom shaft 52 of the metering roller 14 projects. Enclosed within thesub-housing 74 is the rotatable disc 16 containing the coding means 20.The photo pick-up portion 24 is electrically connected with a connectionbox 78, also secured within the housing 74, that provides a plurality ofleads 80 that transmit the signals or pulses generated by the scanningof the coding means 20 to the multiplier and pulse shaping amplifier 26where they are further transmitted for digital display at the counter 28in the windows 30, as seen in FIG. 1. A

suitable source of electrical energy, not shown, is connected with thestructure 22, 24, the pulse shaper and amplifier 26 and the counterdisplay 28.

Provided on the end walls 40 and 42 of the housing 32 are wiper pads 82that may be of any convenient material such as felt or othernon-abrasive composition. Thus, if the housing 32 with its attendantstructure is mounted on the immovable bed part of a milling machine andthe measuring rod 12 is mounted on an adjacent facing side wall of themovable table, the metering roller 14 will rotate about one axis whileengaging the measuring rod 12 positioned in a different axis. As thetable of the milling machine is moved relative to the bed, the movementof the table is imparted to the measuring roller 14 which isconsequently caused to rotate. During such relative movement of thetable to the bed of the milling machine, the rod 12 is wiped clean bythe wipers 82 while the disc 16 containing the coding means 20 isrotated in a one to one ratio with the metering roller 14 which iscaused to rotate by virtue of its pressurized engagement with therelatively moving rod. As the coding disc 16 rotates within the sensingand photo pick-up structure 22, 24, the coding indices or calibrations20 are incrementally sensed and thus transmitted as finite signals orpulses to the multiplier and pulse shaping amplifier 26 from which theyare then transmitted for display at the windows 30 of the digitalcounter 28.

It will be recognized that the yoke 46 permits finite adjustment of themetering roller 14 for line engagement with the measuring rod 12insuring continuous contact without excessive friction. Because of itspivotal movement in response to the precision adjustment of the spring60 at the threaded plug 68, the yoke assures constant positiveengagement between the metering roller and the rod and in consequenceany relative movement between the rod 12 and the metering roller 14 isautomatically translated to rotary motion of the metering roller. Thisrotary motion of the metering roller is then utilized to provide alphaor numeric information at the windows 30 of the counter display 28.

Those skilled in the art will realize that it is unimportant as to theaxial position of the rod 12 or the metering roller 14. It isinteresting to note that no matter what the position of the rod 12, theengagement thereof by the metering roller 14 produces an accurateencoding of information at the sensing and photo pick up 22, 24 whichmay be ultimately utilized at the windows 30. In practice, when thepresent invention is employed on a machine tool, as a milling machine,even though the operating lead screw which is utilized to move the tablemay be worn and have lost motion which would normally result in anerroneous repositioning of the table and the work-piece thereon withrespect to a fixed reference or point, the performance of the presentdevice will enable the operator to see the actual position of thework-piece on the table with respect to such fixed or reference point.Thus, reliance upon the operating lead screw is no longer necessary.

The digital counter 28, is of conventional form, displaying a successivearray of indicia in the windows 30 on the successive impression ofpulses from the shaper 26. The shaper 26 is also of conventional designbeing capable of providing a digital pulse (positive or negative)depending on the direction of movement of the coding disc 16, (i.e. themeasuring rod 12) so that the ultimate indication on the digital displayis the sum or is the actual indication of the extent or degree ofmovement of the machine tool. Further, the shaper 26 or the digitalcounter 28 may be provided with reset means or signal erace means sothat the counter can be originated at a zero position. These devices arewell known in the electronic computer and calculator art andconsequently need not be further described here.

The device is placed in operation merely by having the operator set thecounter 28 at a fixed position, such as the reset position, or observethe initial readout in the windows 30, when the machine is at rest. Inany event, the readout provides the operator with a fixed referencepoint, or starting point, for the machine, since any change in theindicia of the counter neces sarily indicates a corresponding change inthe position of the measuring rod 12. The machine is then operatedthrough its cycle. Thereafter, the operator merely sets the machine sothat the indicia in windows 30 corresponds to the original readout.

Accordingly, the use of unskilled machine operators is made possible bythe present invention. All that is necessary is that the operator of themachine watch the alpha or numeric information displayed at the windows30 to see and assure himself that he has positioned or repositioned thework-piece at the desired location with respect to the preselected fixedreference or point as is displayed in the windows 30. It is no longernecessary to teach a machine operator how to read the Verniercalibrations provided on the lead screw and the table nor is itnecessary to worry that the backlash or wear in the operating lead screwof the machine has produced an erroneous positioning or repositioning ofthe table. When the operator reads the alpha or numeric information inthe windows 30, he knows that if he started with a particular bit ofinformation displayed in the windows and wishes to return the work-pieceto the same measurement point or reference, the lead screw operating thetable need merely be rotated until such time as the relative motionbetween the metering roller 14 and the measuring rod 12 causes thedesired alpha and/or numeric measurement information to appear again inthe windows 30. This arrangement of structure thus enables any fixedpoint or preselected point on the machine table to be positioned andrepositioned and returned relative to another preselected fixed orreference point consistently and accurately, this without concern as tothe inaccuracies or wear of the machine parts.

In FIGS. 5 and 6 an embodiment is shown in which the aforementionedflexible coupling is employed. In these figures, all parts, like thoseshown in FIGS. 1-4, are given like reference numerals and function in alike manner except where otherwise specifically noted. The flexiblecoupling, shown in FIGS. 5 and 6, is given the general numeral 84 andmay be used when the axis of the metering roller 14 and the axis of thescanning disc 16 are not necessarily aligned or wherein freedom ofmovement between the disc 16 and its associated photocell sensing means22 is desired. It may also be used when the yoke 46 is mountedindependently and separately pivotable from the sub-housing 74.

As seen in FIGS. 5 and 6, the interior of the outer housing 32 isprovided with a relatively thick contoured lining 86 having a top wall88, a lower wall 90 and an intermediate wall 92. The shaft 52 of themetering roller 14 extends through the intermediate wall 92 and connectswith a coupling 84 as its input shaft. The coupling 84 has an outputshaft 94 which extends through the wall 90 of the lining 86 and has anextension 96 forming the axle of the disc 16. The output shaft 94 issecured in a bearing 98 within the rear wall 90 so as to be maintainedagainst any movement or vibration. The light source 22 is mounted withinthe wall 90 while the sub-housing 74 is conventionally secured to thewall 90. The adjustment screw 68 and spring 60 holding the yoke 46 isprovided in a through bore extending through the lining 86, as will beobvious. On the other hand, the sub-housing 74 may be secured not to theyoke 46 but may be secured to the outer housing 32.

The coupling 84 is conventional in nature and is adapted to flexiblyconnect the two linear rotatable shafts of the metering roller and thedisc, for conjoint movement while the same shafts may be movable orangularly adjustable relative to each other. The exact nature of thecoupling is not shown since a number of such devices are readilyavailable and are also well known to those skilled in the present art.It will be obvious, however, that the coding disc 16 and the sensingdevice may be thus positioned slightly askew of the axis of the rollermeter so that advantage might be taken of spatial or other operatingconditions which might limit the inline arrangement described inconnection with FIGS. 1-4. Further, the flexible coupling permits theyoke 46 and the metering roller 14 to be pivoted independently of thedisc 16 and its associated light and photocell sources.

, In the embodiment shown in FIGS. 7-9, the apparatus is designed to beutilized on a machine tool which, for example, vibrates excessively orhas some large degree of movement angular to the linear direction of themeasuring rod 12. Notwithstanding the special application, the device asshown in FIGS. 7-9 can obviously function anywhere that the previouslydescribed embodiments will.

Again, like parts are given like numbers and function in like manner asdo those parts previously described. In this embodiment, however, thepivot pin 56 for bolding the yoke 46 is set in a slot 100 having alongitudinal axis normal to the linear direction of the member 12.Simultaneously, the wall 36 of the outer housing 32 is provided with adepending tab or boss 102 adjacent the arm 70. by which the yoke isconnected to the sub-housing 74. The tab 102 is provided with a slot 104having an axis normal to the linear axis of the member 12. A pin 106 issecured within the arm 70 and extends into the slot 104. In this manner,the yoke 46 and the subhousing 74 carrying the disc and photocell codingdevice 22, 24 can be translated relative to the pins 56 and 106 andmovable in the slots 100 and 104 so as to maintain the metering roller14 in constant surface engagement along the tangential contactingportions of the engaging members. This arrangement delimits the possiblerate of build-up of inaccuracies during the movement of the roller 14relative to the measuring rod 12.

FIGS. and 11 show still another embodiment which accomplishes the samepurpose as that of the embodiment shown in FIGS. 7-9. In this case, theyoke 46 carrying the metering roller substantially along its centralaxis transverse to the longitudinal axis of the measuring rod 12 issubstantially balanced in see-saw manner. The adjustable pressure springmeans 60 is located at the center of the yoke 46 and bears directlyabove the axis of the metering roller 14 so that the yoke carries andurges the roller directly against the rod 12. Otherwise, the yoke 46 issubstantially free floating above the measuring rod 12. The housing 32is provided with a relatively thick lining 110 through which areprovided a pair of bores 112, in each of which are secured a pin 114.Each of the pins 114 slidingly fit within a bore 116 formed respectivelyat the forward and aft ends of the yoke 46. The free floating yoke 46 isthus relatively floatable above the rod 12 and is urged thereagainst bythe action of the adjustable spring 60 so that should any movement ofthe measuring rod 12 occur, a corresponding and direct movement of themetering roller 14 would be accomplished.

To illustrate the versatility of the present invention, other changes inthe form of the apparatus are shown in FIGS. 10 and 11. It will be firstnoticed that the wiper pads 82 are set in notches 118 formed within thewalls of the housing 32 and are retained by a plate 120 secured overthem. The wiper pads 82 may thus be made of extremely inexpensivematerial, such as cotton wadding instead of felting and yet be securedon the housing 32 for a long and effective life. A second modificationis illustrated in FIGS. 10 and 11 dealing with the coupling of the disc16 to the shaft 52 of the metering roller 14. Here, the couplingdepicted generally by the numeral 122 may be made as a variable speedclutch or reduction gear system or similar coupling device so that thedisc and the shaft rotate at ratios greater or lesser than the one toone ratio previously described. In this connection, the incrementalmovement of the scanning disc 16 may be more closely calibrated toobtain the digital display in more finite and precise terms.

It will thus be obvious that the present invention provides a simple andeconomical device whereby the movement of a machine tool element may bemeasured and visually displayed with respect to a reference point whichis independent of the machine tool element itthe movable element is.Thus, the present apparatus eliminates any distortion which may occurfrom the wear or other inaccuracies inherent in the machine toolelement.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to a preferredembodiment thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in the artwithout departing from the spirit of the invention. It is the intention,therefore, to be limited only as indicated by the scope of the claimsappended hereto.

What is claimed is:

l. The system for measuring and displaying the movement of a linearlymovable element comprising a measuring member and a rotatable memberangularly disposed thereto and in surface contact therewith,

one of said measuring and rotatable members being displaceableconjointly with the movable element causing simultaneous rotation ofsaid rotatable member,

rotatable coding means flexibly coupled with said rotatable member forrotation thereby and producing a signal indicative of the rotationthereof,

a display device for visually displaying said signal,

a movable support for said rotatable member to move the same intosurface contact with said measuring member,

means housing said coding means separate from said rotatable member,

and adjustable biasing means acting on said movable support to adjustthe extent of frictional surface contact between said rotatable andmeasuring members,

said movable support being movable on said housing toward and from saidmeasuring member,

and means housing said coding means in a stationary position while saidrotatable means moves with said movable support.

2. Apparatus for metering the movement of a movable element comprising ameasuring member fixedly mounted for simultaneous displacement with themovable element,

a metering roller rotatable about its central axis,

a yoke movable toward and away from said measuring member,

said metering roller being mounted in said yoke and movable with respectto and in engagement with said measuring member,

spring means acting directly on said yoke to bias said metering rollerinto engagement with said measuring member,

adjusting means to adjust the tension of said spring means acting onsaid yoke,

a fixed housing containing an annular disc fixed with respect to saidhousing and operatively flexibly connected to and for conjoint rotationwith said shaft,

said metering roller rotatively coupled with said disc,

said disc having a plurality of uniformly spaced apertures annularlyarranged therein and a photoelectric sensor arranged to receive lightpassing through said apertures as said disc rotates,

said sensor producing a signal responsive to the movement of said disc,

and means for visually displaying said signal.

3. Apparatus for measuring the displacement of a movable elementcomprising a measuring member fixedly mounted for simultaneousdisplacement with the movable element,-

a housing fixedly mounted with respect to the movable element,

a yoke pivotally mounted within said housing about an axle extendingtransversely to said measuring member,

a metering roller rotatable about its central axis mounted within andfor movement with said yoke,

spring means acting on said yoke to bias said metering roller intoengagement with said measuring m m ad usting means to vary the tensionof said spring means,

said metering roller having an axial shaft extending therefrom,

a disc flexibly coupled with and rotatable by said shaft,

said disc having a plurality of apertures located therein,

a sub-housing surrounding said disc,

a light source and a photocell mounted within said sub-housing onopposite sides of said disc said apertures creating in said photocell anincremental series of signals indicative of the rotation of the saiddisc, said disc being fixed in relation to said light source whilerotatable relative to said light source,

and visual display means responsive to said signals for indicating theincremental movement.

I 4. The apparatus according to claim 3,

wherein said sub-housing is secured to said outer housing againstmovement.

5. The apparatus according to claim 3,

said adjusting means for varying the tension of said spring means beingon said housing and acting directly on said spring means.

6. A system for metering and measuring the movement of a movable elementcomprising a first housing member movable toward and away from saidmovable element and having a roller follower adapted to engage themovable element and rotatable in correspondence with relative movementtherebetween,

a second housing member having coding means rotatable about a fixed axiscoupling means flexibly connecting the roller follower and said codingmeans for conjoint rotation irrespective of the movement of the firsthousing and roller follower, thereby the relative movement of saidroller follower and movable element is translated into an electricalsignal,

and means directly biasing said first housing member for movement tourge said roller follower against said movable element.

7. The apparatus according to claim 6,

wherein said second housing member is fixed while said first housingmember moves toward and away from said movable element and said flexiblecoupling means enables the roller follower and coding means to rotate atthe same ratio while said coding means remains fixed but rotatable withrespect to said sensing means.

1. The system for measuring and displaying the movement of a linearlymovable element comprising a measuring member and a rotatable memberangularly disposed thereto and in surface contact therewith, one of saidmeasuring and rotatable members being displaceable conjointly with themovable element causing simultaneous rotation of said rotatable member,rotatable coding means flexibly coupled with said rotatable member forrotation thereby and producing a signal indicative of the rotationthereof, a display device for visually displaying said signal, a movablesupport for said rotatable member to move the same into surface contactwith said measuring member, means housing said coding means separatefrom said rotatable member, and adjustable biasing means acting on saidmovable support to adjust the extent of frictional surface contactbetween said rotatable and measuring members, said movable support beingmovable on said housing toward and from said measuring member, and meanshousing said coding means in a stationary position while said rotatablemeans moves with said movable support.
 2. Apparatus for metering themovement of a movable element comprising a measuring member fixedlymounted for simultaneous displacement with the movable element, ametering roller rotatable about its central axis, a yoke movable towardand away from said measuring member, said metering roller being mountedin said yoke and movable with respect to and in engagement with saidmeasuring member, spring means acting directly on said yoke to bias saidmetering roller into engagement with said measuring member, adjustingmeans to adjust the tension of said spring means acting on said yoke, afixed housing containing an annular disc fixed with respect to saidhousing and operatively flexibly connected to and for conjoint rotationwith said shaft, said metering roller rotatively coupled with said disc,said disc having a plurality of uniformly spaced apertures annularlyarranged therein and a photoelectric sensor arranged to receive lightpassing through said apertures as said disc rotates, said sensorproducing a signal responsive to the movement of said disc, and meansfor visually displaying said signal.
 3. Apparatus for measuring thedisplacement of a movable element comprising a measuring member fixedlymounted for simultaneous displacement with the movable element, ahousing fixedly mounted with respect to the movable element, a yokepivotally mounted within said housing about an axle extendingtransversely to said measuring member, a metering roller rotatable aboutits central axis mounted within and for movement with said yoke, springmeans acting on said yoke to bias said metering roller into engagementwith said measuring member, adjusting means to vary the tension of saidspring means, said metering roller having an axial shaft extendingtherefrom, a disc flexibly coupled with and rotatable by said shaft,said disc having a plurality of apertures located therein, a sub-housingsurrounding said disc, a light source and a photocell mounted withinsaid sub-housing on opposite sides of said disc said apertures creatingin said photocell an incremental series of signals indicative of therotation of the said disc, said disc being fixed in relation to saidlight source while rotatable relative to said light source, and visualdisplay means responsive to said signals for indicating the incrementalmovement.
 4. The apparatus according to claim 3, wherein saidsub-housing is secured to said outer housing against movement.
 5. Theapparatus according to claim 3, said adjusting means for varying thetension of said spring means being on said housing and acting directlyon said sPring means.
 6. A system for metering and measuring themovement of a movable element comprising a first housing member movabletoward and away from said movable element and having a roller followeradapted to engage the movable element and rotatable in correspondencewith relative movement therebetween, a second housing member havingcoding means rotatable about a fixed axis coupling means flexiblyconnecting the roller follower and said coding means for conjointrotation irrespective of the movement of the first housing and rollerfollower, thereby the relative movement of said roller follower andmovable element is translated into an electrical signal, and meansdirectly biasing said first housing member for movement to urge saidroller follower against said movable element.
 7. The apparatus accordingto claim 6, wherein said second housing member is fixed while said firsthousing member moves toward and away from said movable element and saidflexible coupling means enables the roller follower and coding means torotate at the same ratio while said coding means remains fixed butrotatable with respect to said sensing means.